1. Field of the Invention
The present invention relates generally to methods for changing internal parameters of implanted devices, such as a cardiac pacemaker, and more particularly to means, such as the use of a vibration generating external device, for generating a programmed response within the implant.
2. Description of the Prior Art
Prior methods for controlling or changing the parameters of an implanted cardiac pacemaker have included the application of a permanent magnet wherein the magnetic field generated causes a magnetic reed switch within the pacemaker to close. This actuation of the magnetic reed switch is then used to activate or deactivate a circuit or to set parameters within the pacemaker. As an example, an output generated by a circuit which is generally inhibited when cardiac activity exceeds a preset rate can be converted by application of the magnet to an output which stimulates cardiac rate at a preset value.
In another method, an external programming device generates pulsating magnetic fields and coded signals which are transmitted to a reed switch within the implanted cardiac pacer. The signal is then decoded by the implanted pacer through detection of the repetitive actuation of the reed switch and provides, in a programmed response thereto, a set of parameters within the implanted pacer. An example would be to change a cardiac pacer from atrial pacing to ventricular pacing or from atrial fixed-rate pacing to atrial inhibited pacing or to change the cardiac stimulating current from 7 milliamps to 5 milliamps.
Although no implant systems responsive to vibration control are known to applicants, prior references using vibration signals have been proposed. In particular, the Summers U.S. Pat. No. 3,672,352 discloses a system for monitoring a condition of a body function or organ or of a device implanted within a body and includes an implanted sensor or transducer connected to a signal generating device. This signal generating device is arranged to generate an audible, visual or heat signal representing the condition of the implanted device, as, for example, the status of the battery charge. More particularly, this signal generating device uses a variation in intensity, such as an on/off code, to transmit information about the condition of the implanted device through the skin to a signal receiver.
Another system is proposed in the Mann U.S. Pat. No. 4,082,097 which presents a system for controlling the charging of an implanted battery. In this patent it is suggested that the battery recharging could be accomplished through the transmission of energy through the skin of the patient. This transmission was described in terms of electromagnetic fields but suggested the possibility that mechnical vibrating waves from an external source could be used to penetrate the skin and recharge the battery.
A similar system is proposed in the O'3 Hara U.S. Pat. No. 4,041,954. Here an electromagnetic generator or a mechanical sound wave generator is utilized to project energy into an implanted receiver which thereupon generates an information signal for external transmission.